issues logging in with prompted credentials

[exaexa]

We saw this problem when the client login is asked for prompting the username & password:

(env) PS C:\Users\bednarek\repos\recodex-feeder> recodex login --prompt-credentials --api-url https://recodex.mff.cuni.cz/api/
Username: bednarek
Password:
╭─ Error ──────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ (400)                                                                                                                │
│ Reason: Bad Request                                                                                                  │
│ HTTP response headers: HTTPHeaderDict({'Date': 'Mon, 12 Jan 2026 09:38:12 GMT', 'Server': 'Apache/2.4.63 (AlmaLinux) │
│ OpenSSL/3.2.2', 'Access-Control-Allow-Origin': '*', 'Access-Control-Allow-Headers': 'headers, Authorization,         │
│ Accept-Language, Content-Type, X-ReCodEx-lang', 'Access-Control-Allow-Methods': 'GET, POST, PUT, DELETE, PATCH,      │
│ OPTIONS', 'X-Powered-By': 'Nette Framework 3', 'X-Frame-Options': 'SAMEORIGIN', 'Vary': 'X-Requested-With',          │
│ 'Set-Cookie': '_nss=1; path=/; secure; HttpOnly; SameSite=Strict', 'Strict-Transport-Security': 'max-age=15768000',  │
│ 'X-Xss-Protection': '1; mode=block', 'X-Content-Type-Options': 'nosniff', 'Referrer-Policy': 'same-origin',          │
│ 'Upgrade': 'h2', 'Connection': 'Upgrade, close', 'Transfer-Encoding': 'chunked', 'Content-Type': 'application/json;  │
│ charset=utf-8'})                                                                                                     │
│ HTTP response body: b'{"code":400,"success":false,"error":{"message":"Invalid Argument \'username\' - The provided   │
│ value did not pass the validation of type \'string\'.","code":"400-000","parameters":{"argument":"username"}}}'      │
│                                                                                                                      │
╰──────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯

No clue what the issue is, other forms of login seem to work just right (we use the API tokens now).

It doesn't seem to be powershell- or windows-specific.